Techniques for modulating carrier signals in order to transmit information between two points are well known. In systems employing frequency modulation, for example, a carrier signal is modulated by changing the frequency of the signal in accordance with an information signal such as a human voice. Amplitude-modulated systems change the amplitude of a fixed-frequency signal in accordance with an information signal. Other modulation techniques have been developed over the years to optimize transmission characteristics, to optimize signal bandwidth, and to overcome noisy transmission environments.
So-called “chaotic” signals provide a particularly interesting, simple, and useful means of modulating information signals in a manner that can increase noise immunity and reduce the power levels needed to transmit information. As explained in the aforementioned application, which is bodily incorporated herein, these signals can be modulated in various ways to transmit information. The modulation bandwidth available when using such techniques, however, has been determined to be generally limited to 10 to 15% of the tank circuit frequency in the transmitting circuit. This limitation is believed to be due to the fact that changing lump parameters in the transmitter causes a certain amount of settling time before the receiver can synchronize with the changed transmitter parameters.
The present inventors have discovered a technique for modulating the transmitting signal in a manner that results in much faster signal stability, thus reducing the amount of time required to synchronize the receiver and increasing the modulation bandwidth dramatically. Other features and advantages provided by the present invention will become apparent upon reading this specification in conjunction with the figures.
The following description begins by reviewing the subject matter of the aforementioned application as a departure point for explaining the principles of the present invention. Circuits, principles and embodiments described in the aforementioned application will be referred generally to as “first-generation,” while those newly presented in this application will be referred to generally as “second-generation” or “improved.” These labels are not intended in any way to be limiting. Moreover, many of the second-generation circuits and principles can be used in conjunction with first-generation circuits and vice versa.